Electromagnetic horn projector



March 10, 1964 M. R. THOBEN 3,124,098

ELECTROMAGNETIC HORN PROJECTOR Filed July 15, 1962 INVENTOR. M YAON R. THOSE N BY OIR.W

HIS A TTO/FNE) United States Patent 3,124,098 ELECTRGMAGLQETIQ HGRW PRUJEQTUR Myron R. Thoben, Anderson, Ind, assignor to General Motors Corporation, Detroit, Mich, a corporation of Delaware Filed July 13, 1%2, Ser. No. 29%,532 Claims. (Cl. 116-142) This inventionrelates to electromagnetic horns and more particularly to an electromagnetic diaphragm horn that has a projector that increases the decibel rating of the horn.

The present invention is concerned with the projector assembly of an electromagnetic diaphragm type of horn which is commonly used as a sound signal on automotive passenger cars. This type of horn is well-known to those skilled in the art and includes a projector assembly which is secured to a power plant that vibrates or reciprocates a diaphragm. The power plant in most cases takes the form of an electromagnet having a coil winding and an armature which is connected with the diaphragm of the horn. In heretofore known electromagnetic horns of the type described, the projector assembly has a spirally shaped air column or sound passage which begins in a chamber located at the middle of the projector assembly and which ends at the mouth or outlet of the projector assembly.

One of the primary objects of this invention is to provide a horn of the type described wherein the beginning of the sound passage takes the form of a chamber which has cylindrical walls but which has one flat wall which is located at substantially 45 to the longitudinal axis of the diaphragm of the horn. With this arrangement, this flat wall is located at substantially 45 to the plane of the diaphragm. It has been found that this flat wall greatly increases the decibel rating of the horn as compared to prior structures which used cylindrical. or spherical surfaces as the beginning of the air column or sound passage.

Further objects and advantages of the present invention will be apparent from the following description, reference being had to the accompanying drawings wherein preferred embodiments of the present invention are clearly shown.

In the drawings:

FIGURE 1 is a plan view of an electromagnetic horn which has a projector made in accordance with this invention.

FIGURE 2 is a view partly in section taken along line 2-2 of FIGURE 1.

FIGURE 3 is a plan view illustrating the internal construction of a part of the projector assembly of this invention and taken along line 33 of FIGURE 2.

Referring now to the drawings, the reference numeral 10 is used to generally designate the power plant of an electromagnetic diaphragm type of born. This power plant 10 includes a metal back shell 12 which supports a coil winding assembly that is not illustrated. The coil winding assembly together with a contact assembly cause an armature 14 to reciprocate. The armature 14 is connected with a metal diaphragm 16 and as the coil winding of the power plant 10 is intermittently energized, the diaphragm 16 is reciprocated all of which is well-known to those skilled in the art.

The power plant 10 carries a projector assembly which is generally designated by reference numeral 18. This projector assembly includes a collar member 20 and a cap member 22. The collar member 20 may be formed as a die casting of a Zinc base alloy. The cap member 22 may be formed of any suitable material but is illustrated in the drawing as being formed of a plastic moldable material such as hard rubber. The collar member 20 and the cap member 22 are secured together by a suitable sealing 3,124,998 Patented Mar. 10, 1964 "ice compound and the collar member 2t) has a rivet 24 which passes through an opening in the cap member and is rivetted over to secure the two parts together. The projector assembly is secured to the power plant It) by a plurality of rivets 26.

The cap member 22 has a spiral air column or sound passage which is designated by reference numeral 28 and which begins at a chamber 30 and terminates at a relatively Wide opening 32. This sound pasage or air column 28 is formed by a spirally extending wall 354. This spirally extending wall forms a part of the chamber 30 the other part being formed by a flat wall 36. It can be seen from FIGURE 2, that the wall 36 is located at substantially 45 to the longitudinal axis of the armature 14 and is therefore located at substantially 45 to the plane of the diaphragm 16. It can be seen from FIGURE 3 that the fiat surface or wall 36 faces in the direction of the portion 28a of the spiral passage 28.

The collar member 2% has a spirally shaped wall 38 which matches and engages the spirally shaped wall 34 of the cap 22 to form an air column or sound passage. The collar 20 has a central opening 40 which follows the contour of the wall portion 34 that defines the chamber 30. It thus is seen that as the diaphragm 16 reciprocates, sound Waves are generated in the chamber 30 which move outwardly through the air column and which are reflected off the flat surface 36. It has been found that this flat surface 36 greatly increases the decibel rating of the horn as compared to heretofore known horn projectors wherein the surface equivalent to surface 36 is spherical or arcuate. In other words, in heretofore known horn projectors, the chamber 3% has been formed entirely as a sphere or by arcuate surfaces and the improvement of this invention is therefore in the providing of a flat surface 36 which is located substantially 45 to the plane of the diaphragm 16.

While the embodiments of the present invention as herein disclosed, constitute a preferred form, it is to be understood that other forms might be adopted.

What is claimed is as follows:

1. An electromagnetic horn comprising, projector means having a chamber, and reciprocable diaphragm means facing said chamber, an outlet passage communieating with said chamber having an axis which is located substantially parallel to said diaphragm, at least one wall of said chamber being substantially flat and being located at an angle of substantially 45 to the plane of saiddiaphragm means.

2. A horn comprising, projector means having a cham-- her, and a diaphragm reciprocable with respect to said projector means and facing said chamber, an outlet passage communicating with said chamber having an axis which in located substantially parallel to said diaphragm, said chamber having a flat wall which extends at substantially 45 to the plane of said diaphragm.

3. A horn comprising, projector means having a spirally shaped air column beginning in a chamber and terminating at an outlet, and diaphragm means reciprocable with respect to said projector means and facing said chamber, said chamber having at least one wall thereof which is flat and located at substantially 45 to the plane of said diaphragm means, the beginning of said air column having an imaginary axis which if extended would intersect said wall.

4. A projector for an electromagnetic diaphragm type of horn comprising, a housing defining a spirally shaped sound passage which increases in size from a chamber to the outlet of said projector, said chamber having a wall section which is fiat and which is located at substantially 45 to the longitudinal axis of said projector, the axis of said sound passage lying in a plane which is substantially parallel to said diaphragm.

5. A projector for an electromagnetic horn comprising,

3 housing means defining a spirally shaped air column having a chamber at the inner end thereof and an outlet, said chamber having a wall section which is flat and which is located at an acute angle to a longitudinal axis of said projector, said wall section facing the beginning of said spirally shaped air column.

6. A projector assembly for an electromagnetic horn comprising, a collar member, a cap member, said collar member and cap member defining a spirally shaped sound passage beginning in a chamber and terminating in an outlet, said chamber having a wall portion which is substantially fiat and which is located at an acute angle to a longitudinal axis of said projector, said wall portion facing the beginning of said spirally shaped air column.

7. An electromagnetic diaphragm horn comprising, a power plant including a reciprocable armature, a projector assembly having a spirally shaped air column beginning in a chamber and terminating in an outlet, said projector assembly being secured to said power plant, and 21 diaphragm secured to said armature, said armature being located in alignment with said chamber, said chamber having a wall section which is substantially fiat and which is located at substantially 45 to the longitudinal axis of said armature, said wall section being located at an acute angle to a longitudinal axis of said projector assembly.

8. An electromagnetic diaphragm horn comprising, a power plant including a reciprocable armature, a projector assembly having a spirally shaped air column beginning in a chamber and terminating in an outlet, said projector assembly being carried by said power plant, and a diaphragm secured to said armature, said armature being located in [a alignment with said chamber, said chamber having a wall section which is substantially flat and which is located at an acute angle to the longitudinal axis of said armature, the spirally extending axis of said spirally shaped air column being located in a plane which is substantially parallel to said diaphragm.

9. A horn comprising, a power plant, a project assembly having a spirally shaped air column beginning in a chamber and terminating in an outlet, said projector assembly being secured to said power plant, and a diaphragm reciprocated by said power plant, said chamber having a Wall section which is substantially fiat and which is located at an acute angle to said diaphragm and at an acute angle to a longitudinal axis of said projector assembly.

10. A projector assembly for a horn comprising, housing means defining a spirally shaped air column having an outlet, a chamber defined by said housing means, said chamber having an outlet connected with the inlet of said spirally shaped air column and having an inlet, the plane of the inlet of said chamber being located substantially normal to the plane of the outlet of said chamber, said chamber having a Wall section which is fiat and which is located at an acute angle to a longitudinal axis of said projector assembly.

References Cited in the file of this patent UNITED STATES PATENTS 1,935,788 Critchfield Nov. 21, 1933 2,352,467 Borden June 27, 1944 2,677,875 White et al. May 11, 1954 

1. AN ELECTROMAGNETIC HORN COMPRISING, PROJECTOR MEANS HAVING A CHAMBER, AND RECIPROCABLE DIAPHRAGM MEANS FACING SAID CHAMBER, AN OUTLET PASSAGE COMMUNICATING WITH SAID CHAMBER HAVING AN AXIS WHICH IS LOCATED SUBSTANTIALLY PARALLEL TO SAID DIAPHRAGM, AT LEAST ONE WALL OF SAID CHAMBER BEING SUBSTANTIALLY FLAT AND BEING LOCATED AT AN ANGLE OF SUBSTANTIALLY 45* TO THE PLANE OF SAID DIAPHRAGM MEANS. 